order to talkthin-plateweirs/ sharp crest weirs parshall flume no throatedflumes long-throatedflume...
TRANSCRIPT
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Water Measurement Techniques, Water Price and Water Fee collection
Ding Kunlun
Beijing, 11 April 2018
Training for YPs of Asia on Performance
Assessment of Irrigation Systems
1. Water Measurement Techniques
2. Irrigation Water Price & Fee Collection
Order to Talk
1 Water Measurement TechniquesThe purpose of water measurement is:
l to make water supplier be able to supplywater to users according to their demand and,
l to supply water to agricultural field withplanned program and proportionally, and
l to serve volumetric water tariff collection
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The purpose of this part is:
l to understand water measurement facilities inorder to provide a base of selecting watermeasurement techniques for irrigation systems
l to increase the level of irrigation monitoring andwater management in a irrigation district.
In the canal irrigation district:
The water measurement is carried out at:
Measurement location Purposes
at the main canal to control the water supply
at the inlet of the branch canal to distribute the inflow
at the inlet of the tertiary canal to estimate the total amount ofwater, to get water fee
Present Condition of Irrigation Water Measurement in
China
➢better in big reservoir irrigation systems than in small-medium sized irrigation systems
➢better in canal irrigation systems than in well irrigation systems
① Current-meter/flow meter
② Water measurement with canal structures
③ Special water measurement equipment
④ Float measurement
Water measurement on open canals
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① Current-meter/flow meter
Electro-magnetic recorder Wave current meter
Ultrasonic current meterPropeller current meter
Measurement points
Relative depth of the measurement points
1 0.62 0.2, 0.83 0.2, 0.6, 0.85 0.0, 0.2, 0.6, 0.8, 1.0
The relative depth is the ratio of device depth to the total waterdepth of water of the vertical line
Measurement point with flow meter
Main canals Water depth/
m
>3.0 1.0-3.0 0.8-1.0 <0.8
method 5-point 3-point 2-point 1-point
Branch, lateral and field canals
Water depth/
m
>1.5 0.5-1.5 0.3-0.5 <0.3
method 5-point 3-point 2-point 1-point
Method used with flow meter for different water depthMean velocity of the measurement line
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② Water measurement with canal structures
Canal structures used for water measurement must meet thefollowing conditions:
(1) The structures have no damage, no deformation, nodelaminating and no seepage.
(2) Adjusting and lifting equipment should be in a well andcomplete condition, the gate is not skew and distortion, the edgeand the sliding channel of the gate can be closely matched.
(3) There is no sediment and silting within, in front of andbehind the gate, there is no other matters stopping water.
(4) Requirements for hydraulic calculation should be met, headloss is not less than 3 cm, the submergence degree is not biggerthan 0.9 in submerged flow.
Types of canal structures for water measurement:
◆ Standard canal cross-section
◆ water gate and culvert
◆ Water measurement with aqueduct
◆ Water measurement with invert siphon
◆ Water measurement with drop chute (steep flume)
◆ Standard canal cross-section
lLined straight canal
section
lCalibrated by flow meter
for Q-H curve
lUnder free flow conditions
◆ water gate and culvert
Q: can be calculated
with different
formula and
calibrated by current
meter
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Fig. 8. Water measurement and distribution gate of Venturi short tube
◆ water gate and culvert◆ Water measurement with aqueduct
Q: can be calculated by uniform
flow or calibrated
◆ Water measurement with adverse siphon
Q: can be calculated by
formula as above and
calibrated by current
meter
◆ Water measurement with drop chute (steep flume)
Q: can be calculated by
formula as above and
calibrated by current
meter
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③ Special canal water measurement equipment
Thin-plate weirs / sharp crest weirs
Parshall flume
No throated flumes
Long-throatedflume
water measurement sill
Parabolic flume for U-shape canals
Flow-divided discharge meter (simply called divider)
Water distributor
Thin-plate weirs / sharp crest weirs
The ratio of the
plate thickness to
the water head
above the weir is
less than 0.67
Discharge formula of long-throated flume with different
throateded cross-sectional shapes
Throat cross-section shapeYcQ-h relationship
✓Rectangular
✓Triangular
✓Trapezoidal
✓Parabolic
✓Compound
Parshall flume
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Parshall flume
Parshall flume,
discharging 62
ft3/s under free-
flow conditions.
Parshall flume
No throated flumes
Free flow:
Submerged
flow:
Fig.2. Structural diagram of no-throateded flume
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No throated flumes
Fig.3. The structure of long-throateded flume
Control section
Variable spread length
Long-throated flume
L=1.0-1.5 Hmax
Conpare with long-throated flume: No Lateral contraction
water measurement sill water measurement sill
ultrasonic
Data log
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(a) Long-throated flume
(broad-crested weir)
under construction
(b) The long-throated
flume (broad-crested
weir) in use
water measurement sill Parabolic flume for U-shape canals
Fig. 7. The structure of water distributor
Flow-divided discharge meter (simply called divider) Water measurement in well irrigation districts
Mainly those used for pipelines
1. Directly measuring water quantity2. Recording time method3. Recording electricity method4. The combination methods of (1) and (3), or
(2) and (3)5. Short pipe method 6. venturi meter.
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venturi meter
H
D
DY
X
Trajectory Methods
(1) Vertical pipe method (2) horizontal pipe method
Q = 5.01d1.99h0.53 (14-7)
where:
Q = rate of flow, gal/min
d = inside diameter of the pipe, in
h = height of jet, in
Water measurement instrument and device
◼ Water level device
◼ Water meter
◼ Pressure-difference flow meter
◼ Electro-magnetic flow meter
◼ Ultrasonic flow meter
◼ By-pass flow meter
◼ Propeller flow meter Water table meter (sensor and recorder)
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Ultrasonic flow meter Water meter
Electro-magnetic flow meter
Ultrasonic flow meter
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Means to get the data To get the data
Accuracy of water measurement
Water measurement error requirement:
✓ 5% for water meters
✓ 8% for special structures (weirs)
✓ 10% for canal structures (gates, culvert etc.)
1. The design of the water measurement devices should be
included in the planning of the irrigation system. The
installation of these devices should be determined
according to the local conditions as well as be convenient
for calculated water fee from the amount of water. Normally
the lowest level of the device should be installed at the
inlet of the quaternary canal. It is better to measure the
inflow rates for each farmstead/village/group.
Suggestions of Choosing Water
Measurement
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2. The functions of the chosen devices should be
checked if the hydrology and hydraulics requirements
of the canal or pipe are satisfied when the water
measurement devices are determined. These
functions include the range of the measuring, the
limitation of non-submersion, sensitivity, precise, the
abilities of transportation sand, the abilities of passing
float, requirements of water table and water head
loss.
Suggestions of Choosing Water
Measurement 3. When the devices are satisfied for the conditions
mentioned above, it should be also installed
easily, low cost, able to anti-different disturbs
and with easily manage and maintenance.
4. The choosing of the devices should be determined
according to the different objectives of the
measurements, the differences of the canal
sections and/or differences between the pipe
sections and capacity of the water flowing in the
pipe.
5. It is first choice to use the exist structures in the canal
for the water measurement if the measuring precise can
be satisfied. In order to ensure the measuring precise and
other hydrology and hydraulics requirements, it might be
necessary to repair in some parts of the construction or
reform it. And the water table recorders are also necessary.
However, the comparison for economic indicators that it is
reasonable because the investment for building new water
measurement devices is saved and there is no extra
water head loss.
“Standard of Water
Measurement for
Irrigation Canals”,
GB/T 21303-2016
References
National standard of China
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2 irrigation water price and water fee collection
PAY or NO PAY?
ATP or WTP?
Irrigation Water Price----Not only an economic issue, but a social, political, …issue!
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Concepts of “irrigation water
price” used in China
✓“Full cost recovery” price
✓“Operation cost recovery” price
✓“Adopted price” in practice
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➢Full cost recovery: including depreciation of the I&D
structures, operation cost, staff salary, daily R&M.
➢Operation cost recovery: as the full cost recovery but
not including depreciation.
➢Irrigation water price adopted in practice is different
at different locations and systems in China, considering
the farmers’ ability to pay (ATP) and WTP.
➢Water fees are collected by the WUAs or by the
villages, which are handed over to the management
agency and keep part of it for O&M of farm canals.
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➢Target: Gradually to achieve that irrigation
water price should be determined based on the
“operation cost recovery” . Currently, one
comprehensive program on agricultural water
price reform is going on, to achieve this target
within a period of 10 years from 2016.
➢Before the target achieved, financial subsidies
is required to keep good O&M conditions of
I&D .
Overview in China
✓On average, the irrigation water price is only cover 30%-
50% of the supplying cost;
✓ For about 25% large scale irrigation systems and 65%
medium scale systems, the “operation cost recovery”
price is not calculated and authorized;
✓ The rate of water fee collection is about 70%;
✓ 40% of the management agencies/bureaus of irrigation
systems can not have sufficient budget to cover their
O&M cost.
59Overview on World Irrigation Water Price
1、Policies of incentive and subsidy is popular
➢Agricultural irrigation is key to food security and base of
country’s development.
➢ Volumetric water price and area-based price, or combined.
➢E.g. In Spain, combined method was used, i.e.. Charge some
amount based on area and extra fee charged by volume.
➢ In Israel, it is charged at “supply cost” price and ladder water
price is used.
➢Different water price used by different suppliers / systems.
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2、Irrigation water price
➢In Japan, Agriculture is the biggest user,
charging water tariff basically by area.
➢ In US, charging at a water price based on the
water supply / production cost, and making
different prices based on volume used to encourage water saving.
➢ In Spain, again, volumetric, area-based and
combined all are used.
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➢ In Mexico, Water prices are different for different crops
and in different regions. Water price is low for grain crops
and high for cash crops, e.g., at 0.45 $/m3 for strawberry
that is 15 times of that for grain crops, reflecting the
supportive policy to food security.
➢ In Japan, water price is only 0.01 $/m3 in east coast
area and at highest of 0.035 $/m3 north inland areas.
➢ In Romania, water prices are 0-20.34 $/m3, depending
on the water supply cost.
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➢ In China, area-based and volumetric, and
combined tariff used
➢ Irrigation water price is from 0-0.1 $/m3.
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World Irrigation Water Price
➢ What is the irrigation water price in
your country?
➢ How to collect water fees in your
country?
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THANK YOU